The present invention relates generally to the field of electric control devices.
Control devices of a somewhat similar character to that of the present invention have heretofore been generally known from U.S. Letters Pat. No. 3,436,530, issued Apr. 1, 1969; and the present invention constitutes an improvement over the control device of this patent, and includes unique and improved features of operation which expand the scope of usefulness into fields wherein control devices such as shown in the above mentioned patent cannot be used.
Briefly, the above noted patent is directed to a control device for preventing unauthorized use of a machine and contains a key-counter unit having operation counter means therein and which will form an electronic interlocked circuit which is designed to operate as a key, when plugged into the control device, to permit use of the machine by authorized personnel, and which will count or register in the key-counter the number of operations performed and chargeable to the holder of the particular key-counter.
The present invention provides an improved concept which overcomes and solves certain problems which are inherent in the key-counter such as conventionally known according to the above noted patent. One of the disadvantages of the conventional key-counter is that if it should become lost or surreptitiously acquired, the unit could be used by unauthorized personnel to obtain unauthorized productive use of the machine. In the present invention, this possibility is minimized to the extent that should a key-counter be used by unauthorized personnel, it could be used only for obtaining a limited number of productive operations of the machine or instrumentality. For this purpose, there is provided in the key-counter unit, which may be in addition to the usual counter, a measuring device which will function to measure the machine operations, and which may be "charged" or preset for a predetermined number of operations, and when the set number of operations have been used will function in a manner to terminate the machine operation and will render the key-counter ineffective for further use. A keycounter which has thus been discharged by virtue of having used it to obtain the preset number of operations may either be recharged for the required number of operations or may be replaced by another fully charged unit. It will thus be appreciated that if a key-counter having this improved concept were lost, it could only be used to obtain a limited number of operations of the machine.